Pen



FIG. 1 is a side, top, perspective view of the pen;

FIG. 2 is a left side view thereof, the right side view being a mirror image thereof;

FIG. 3 is a top view thereof;

FIG. 4 is a bottom view thereof;

FIG. 5 is a front view thereof; and,

FIG. 6 is a rear view thereof.

The broken lines shown in the figures are included for the purpose of illustrating environmental matter and form no part of the claimed design. 

The ornamental design for a pen, as shown and described. 